Maria Tyler has drowned. Her worried husband, Robert Tyler, is sitting at the police station and shows the latest underwater photos he has taken of her. He blames himself for having been diving so deep with her. He says she’s promised not to go deeper, but she had. He could not follow her and now he is sad that she did not survive.
Something arouses the suspicion of the police officer. He asks his friend, Mike Nelson (Lloyed Bridges), in to help him.
The plan is that Mike goes diving with Robert Tyler at the same place his wife has died. He made him believe it would be possible to discover the body with the help of a newly developed kind of oxygen which makes it now possible to dive this deep. Under water the plan works. Tyler gets nervous and tries to flee taking the boat and trying to kill Mike by running him over with it. Mike dives and puts his scuba into the propellers of the boat. The boat is stopped, they fight and Tyler is giving up.